Open flash application
Choose flash document.
Set the size as per your requirement and keep the frame rate at 24 FPS.
Import to stage any shining object. ( ctrl + R ) OR goto file menu and choose the import option.
Align the image vertically and horizontally center ( ctrl + K ).
Name this layer Image. Create a new layer above the image layer and name it gradient.

Draw a thin rectangle on the gradient layer. Height of the rectangle should be little wider than the width of the image. Fill style linear gradient. Copy the settings as shown in the image below.

Click frame 100 on gradient layer press F6 to insert keyframe. Move the gradient from top of the image ( mobile phone in our case ) to the bottom of the image. Create motion tween between frame 1 and 100.

Above the gradient layer add one more layer and name it mask. On the mask layer with the help of pencil tool or brush fill up the area where you want to create shining/mask effect. Look at the image below.Right click on this layer and choose mask from the options.

Test your movie.